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Seismic Performance Assessment of Monopile Offshore Wind Turbines by Endurance Time Method

Akbarzadeh, Mohammad Reza | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55763 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Esmail Pourestekanchi, Homayoon; Tabeshpour, Mohammad Reza
  7. Abstract:
  8. The rapid development and growth of the offshore turbine industry has led to the construction of offshore wind farms in earthquake-prone areas, and due to the shape of the structural system, which consists of a long cylindrical tube with a heavy mass on top of it, this structure is a sensitive structure. It has a dynamic behavior, and many environmental loads such as wind load, wave load, current load, and earthquake load in seismic areas are dynamic in nature. In this research, it investigates the seismic dynamic behavior of 5MW offshore wind turbine using the ISO-19901-2 standard and the Endurance Time method. In the modeling of this structure, Soil Structure interaction and Fluid Structure interaction is considered. Also, wind and wave forces have been used dynamically. First, the structure is analyzed with non-linear dynamic analysis using ISO-19901-2 standard spectra and FEMA-P695 Fairfield earthquake records, and then the responses are Compare with different damage levels. Finally, with the Endurance time Records, nonlinear dynamic analysis is performed for the Different Hazard levels and the Response are compared with the Response of the previous step analysis. In the last step, by performing incremental dynamic analysis and providing a framework for estimating the dispersion of earthquake responses using the Endurance Time method, the effects of scour in the response and fragility of offshore wind turbines in Medium-dense and dense sand soils have been investigated.The results showed that the Endurance time method can obtain the responses by properly estimating the mean and dispersion. It has also been shown that in the offshore areas of the Persian Gulf, which was considered in this research, Fairfield earthquakes do not cause structural damage to wind turbines at the Hazard levels suggested by the ISO-19901-2 standard, and the damage in some cases is Serviceability limited State(SLS) will occur.It was also shown that the vulnerability of the structure can increase significantly with the increase in scour depth, and even in some limit states of operation before the earthquake, the structure violates the limit conditions under the conditions of waves and wind, and also with the increase of soil resistance, the possibility of damage will also decrease
  9. Keywords:
  10. Offshore Wind Turbine ; Endurance Time Method ; Fragility Curve ; Nonlinear Analysis ; Incremental Dynamic Analysis ; Monopile Substructure ; Seismic Performance ; Seismic Assessment

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